My auto hubs are not locking automatically anymore. About two weeks ago, I had run the truck in 4hi and noticed some clunking sounds coming from the hubs after I went back to 2wd. Since then, with the truck parked and idling, I can shift into 4hi and can feel that the driveshaft is engaged, but I can hand spin the axle shafts, meaning the hubs are not locking. I can manually lock the hubs however. What do you think this clunking sound was that I was hearing? At the time, I had thought it was maybe torque-bind. I reversed a few feet, then didn't have the sound anymore. Ever since then, the hubs don't auto lock anymore.